How much power do I lose because of harmonics? Do I pay for harmonics on my power bill?

A very common question is how much power do I lose because of harmonics, and do I pay for harmonics on my power bill. Let's back up and talk about power in general what we pay on our power bill. 

There's multiple different things that we pay for. One is work, which is Watts we know that we pay for watts, kilowatt hours. We'll talk about that, but work that we do with watts is things like lifting an elevator, moving a motor things like that creating the things that actually do work. The second thing is vars. We call vars reactive power or sometimes we call it imaginary power or magnetic power. Magnetic power allows a motor to spin, but once you overcome friction you're not really doing work. You're just creating a magnetic field. 

Then there's VA. VA is a combination of volts times amps. Volts times amps gives us apparent power, which is a combination of watts and vars together. We'll talk a little bit about that in the power triangle and how that relates to power factor. Then the final part here is harmonic, so it's not watts. It's not vars. But it is related to VA and specifically it's related to the amps. 

Let's take a look at the power triangle but in a three-dimensional version. If we look at on the X-axis, we have kilowatts on the Y-axis we have Kvar, and on the hypotenuse we have kVA and this D here (on the slide) stands for displacement. What that means is that's the two-dimensional, but basically 60 HZ part, of your apparent power. okay now let's add in harmonics. It's not Watts. It's not vars. it goes almost like in the third dimension, in this Z-axis. If I have a lot of harmonics notice how my KVA total now becomes a lot bigger. When I look at the KVA, which again is volts times amps, my current has gone up by adding in these harmonics. If we're going to eliminate kvar here we get closer to kVA equaling kilowatts. That's basically when we do things like power factor correction to get rid of the reactive power from inductive loads. If we're going to reduce harmonics here, that's going to reduce this KVA total. So in reducing 

harmonics here or Kar here we're not really changing the watts at all. We're just changing the KVA. That's really important to understand because what do we pay for on our bill? On our bill we pay for kilowatts or the amount of power that we're using. For commercial customers or large industrials we pay for a kilowatt demand. There's lots of information in our videos about that. There's kilowatt hours which is basically kilowatts over time. so these two are directly related. 

The third part which is related to KVA is based on the power factor and the power factor is kilowatts over KVA. I'll draw that out for you in a minute, but for the 60 HZ part the utilities only bill based on the displacement power factor. This is important. Where does this leave harmonics? Let me draw this out for you and explain it on that three-dimensional chart. 

If we take a look at again on the X-axis is kilowatts, on the Y-axis is kvar, and here's kVA. If the utility doesn't bill us for power factor penalty (and again power factor equals kilowatts divided by kVA)

If the power factor was one for example, our kVA and kilowatts would be equal. The kVAR would be zero. If they don't build us for kVA, and they don't build us for power factor issues with extra kVAR then this becomes irrelevant. they only bill us on kilowatts and kilowatt hours, so kilowatt demand and kilowatts over time. If we added in this third dimension, which again is our harmonics, how does that affect our kilowatts? It really doesn't except in the same way that the vVAR does, and I'll explain that in a minute. 

But it really doesn't affect us. What it does effect is this bigger KVA here, which is KVA total. If we're 

affecting KVA total how does that affect our power factor? Our power factor total is kilowatts divided by KVA total. As you can see since KVA total is bigger than this this other KVA our power factor goes down. I'll reinforce the fact that utilities bill on this power triangle. They bill on that power triangle. They don't bill on the harmonics. 

They're not going to bill you for harmonics. Where this does come into play though there is a there is a small little caveat on all this. If I have a transformer, and I have some cable length and stuff. And, I put a motor on and have current flowing through my system, what does that current do? It affects my load. I'm paying for kilowatts that I'm using to power the load but I'm also paying for the losses along the way through the transformer, through the cables. The I²R = watts, or kilowatts.

When I look at this then I am paying for losses that come down through here for my kVARS and I'm also paying for my losses according to my harmonics. As I mentioned before because KVA is proportional to current any additional current on my system creates additional losses. But a lot of people ere exaggerate that and say that those losses are huge when in fact there're somewhere in the neighborhood of 1% to 4%. as maximum numbers for a typical power system. 

As we look at that, and basically consider Power Systems and how that affects us there's losses in the actual cables and conductors and transformers and so forth, but there's another loss that comes in motors especially. That's where we have things like negative sequence currents. But again, these numbers are very small compared to your overall losses on Power Systems. Again we're in the 1% to 4% range. I've been told that essentially lubricating a motor probably makes up more of a difference than the losses that you get from something like this. 

At the end of the day, how do harmonics affect your power bill? They don't directly affect it because we're billed on power factor displacement which is 60 HZ. The only way harmonics can affect your bill is a little bit directly, but more indirectly is through the losses. And those numbers are in the 1% to 4% range. If you put a harmonic filter on for example and you eliminate all your harmonics you can save 1 to 4%. You can't save 20% of your bill by just getting rid of the harmonics. But in the same way you could get rid of a power factor penalty and save 20% of the money for your bill, you can release some of the money when you do power factor correction with harmonic filters, just not the harmonic part of it. It's all related but just make sure you understand that the part on your bill that you're going to save is losses or power factor compensation. Because harmonic filters do both power factor and harmonics, sometimes there's money to be saved but not from the actual kilowatts or kilowatt hours. It all seems a little confusing but it's really not that bad if you think through it